1. Field of the Invention
The present invention relates to an information recording medium that is used for an optical recording and reproducing apparatus, which reads out information from the information recording medium with making the information recording medium move relatively, particularly, relates to an information recording medium having a read only area from which information can be read out together with a recording and reproducing area in which information can be recorded and from which the information can be reproduced.
2. Description of the Related Art
Until now, there is provided an information recording medium in a shape such as disciform, card and tape as a system of optical information recording medium, which is used for reading out information from the information recording medium that is made to relatively move. On a basis of recording or reproducing mechanism, such an information recording medium is divided into two types; one is a read-only type and the other is a recording and reproducing type (including recordable type and over-writable type). In other words, the former-type recording medium is prerecorded with information and forwarded in a market, and then a user just reproduces the information from the former-type recording medium. The latter-type recording medium is forwarded in a market without recording information. A user newly records information in the latter-type recording medium, and then the user reproduces the information from the latter-type recording medium.
On the contrary, in accordance with advancing multimedia in the world, it is increasing that a copyright is infringed by an electronic method and resulted in a remarkable problem. Consequently, it is required for even a recording and reproducing type information recording medium, which can be recorded by a user freely, to embed a specific code, which can not be rewritten by a user, in an information recording medium so as to protect a copyright from such infringement.
From the point of view of such a copyright protection, there has been provided various kinds of information recording mediums. Each of them has two areas together; one is a read only area that is recorded with permanent data, which can not be rewritten, and the other is a recording and reproducing area that is recordable (or a recording and reproducing area that is rewritable repeatedly). It is popular that an information recording medium, for example, is constituted by a read only area, which is composed of a pit array and prerecorded with a specific data, and a recording and reproducing area, which is composed of a continuous substance of grooves. A phase change type information recording medium such as a DVD-RAM (Digital Versatile Disc-Random Access Memory) and a DVD-RW (Digital Versatile Disk-ReWritable) has been put into practice. A user records information in a recording and reproducing area of such an information recording medium as user recording.
Incidentally, it is studied that a method of recording a permanent data by using a wobbling groove in conjunction with constituting a read only area by a groove instead of a pit array. If the permanent data is recorded by a wobbling groove as mentioned above, the original permanent data can be distinguished from altered permanent data, which have been forged by a person of counterfeiting, and resulted in disclosing a fact of infringing a copyright easily because such a person of counterfeiting can record the permanent data only through the phase-change recording method. In other words, he can record the permanent data by the pit-array recording method, which uses difference of reflectivity.
Accordingly, constituting a read only area by a groove can advance copy protection more than by the conventional pit-array recording method.
The inventor of the present invention has manufactured an above-mentioned information recording medium actually as a trial and reproduced the information recording medium, and then he recorded the information recording medium with information and reproduced the information. Consequently, he found some problems related to reproduction.
FIG. 19 is a plan view of an information recording medium 90 manufactured as a trial. The information recording medium 90 is composed of a read only area 93 and a recording and reproducing area 94. Further, both of the read only area 93 and the recording and reproducing area 94 are constituted by a groove. The read only area 93 is recorded with a specific code data for copy protection by a wobbling groove and the recording and reproducing area 94 is recorded with a location data, which is a reference data that is essential while recording, by a wobbling groove. When recording the specific code data and the location data, a shape of groove is optimized. In the read only area 93, the shape of groove is optimized so as for an output of the specific code data to be maximum. In the recording and reproducing area 94, user recording is performed while reading the location data and the shape of groove is optimized so as for a reproduction error rate at the time to be minimized.
The information recording medium 90 constituted as mentioned above has been loaded in various kinds of recording and reproducing apparatuses and operated. However, some problems arise such that traversing two areas has hardly performed smoothly and tracking has been out of control. In other words, when trying to read a location data in the recording and reproducing area 94 after reading out a specific code data for copy protection from the read only area 93, tracking has deviated off the control frequently.
This is caused by that functions of respective areas are different from each other. Further, characteristics of previously recorded data are also different from each other. Consequently, it is found that groove shapes of two areas are different from each other if the functions and characteristics are optimized in accordance with respective purposes and continuous reproduction with traversing through both areas can not be conducted.